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Fishy Friday: Lobster test

In a concerted effort to talk more about one of my main areas of work, I’ve decided to do a weekly blog dedicated to FISH! It might be fisheries biology, management of stocks, how to survey cockles, sustainability, a person or book, or issues in the news: anything, really, that is either topical or currently on my mind.

For the first #fishyfriday post, I’m going to talk a bit about some work I was involved with a couple of years back. And when I say “talk” about it, I mean literally…

This is a demonstration of a “pregnancy” test for scrubbed lobsters (animals who’ve had their eggs removed so that they can be landed and passed off as non-egg-bearing). There’s also a bit of lobster biology 101 – how (if you were so inclined) might you discern an American/Canadian lobster (Homarus americanus) from its European cousin (Homarus gammarus)? How does one “sex” a lobster (other than “carefully”, natch)?

The “pregnancy test” I talk about was originally developed in the States by Karlsson & Sisson in the 70s, so it’s not new. In fact, the main “ingredient” is the common biological stain haemotoxylin, which is frequently used to prepare thin sections in biological microscopy. However, although it’s routinely used in the States it’s only recently that the test has been used for enforcement purposes in the UK. It has, however, been adopted by several IFCAs and successfully used as evidence in a prosecution on the East coast. As such, it acts as a deterrent to the (very few) fishermen who engage in “scrubbing”.

The main barrier to preventing the practice now is legislative: although much of the inshore UK lobster grounds are covered by IFCA byelaws prohibiting the removal of egg bearing lobsters, national protection is (unbelievably) not provided, so enforcement agencies can only stop “scrubbing” inside certain IFCA Districts – and they have to prove the animals were not caught outside. In contrast, American fisheries law looks much less kindly on the practice.

It should be said that the majority of fishermen I’ve met are totally against scrubbing, and will v-notch* and return berried/egg-bearing lobsters to protect the breeding stock.

One of the main ingredients is Industrial Methylated Spirits – methyl alcohol. The main difference between this and “regular” methylated spirits is it doesn’t have that weird purple dye; however, as an alcohol, we had to apply for a special license from HMRC to say what it was being used for (i.e. not for consumption) in order to be able to order supplies

The alcohol is used to rinse the swimmeret/pleopod and as a solvent for the stain ingredient, haematoxylin

Haematoxylin is a *really* good stain. Ergo, a pain if you get it on anything; skin, clothes. I dug out my lab coat for use during testing!

If there’s a positive result, the test is repeated on a second pleopod from that lobster. Only if that is also positive is there considered to be a potential infringement.

Both pleopods from a “fail” are taken, preserved, and then analysed under a high powered microscope. This provides the ultimate check and insurance against a false positive result: scrubbing causes damage to the fine hairs (setae) on the pleopods which is clearly visible under a microscope. Looks like split ends…

There’s a small chance that a naturally-shed lobster might yield a false positive – but the microscope examination catches these; you can see the empty egg casings (and no damage to the setae hairs).

*”V notching” is the practice of clipping a v-shaped… well, notch… in a female lobster’s tail. Here’s a picture of a berried (American) lobster with a “v notch” in her tail. This is compulsory in some US fisheries when berried lobsters are caught, but generally voluntary over here. The lobster is returned to the sea, and thus gets the chance to release her eggs. Normally, it takes a while for the notch to disappear over at least one moult, so she may get another shot at reproducing. It’s illegal (UK included) to land a lobster with damage to the tail indicating it has been v-notched.